1. Field
The present disclosure relates to a nitride semiconductor, and more specifically, to a substrate having a hetero-structure (hereinafter, referred to simply as a “hetero-substrate”), a method for manufacturing the same, and a nitride semiconductor light emitting device using the same.
2. Background
A light emitting device represented by a light emitting diode (LED) provides various colors through a p-n junction diode which converts electrical energy into light energy by controlling a compositional ratio of a compound semiconductor produced using a compound of Group III and V elements on the periodic table.
Nitride semiconductors have attracted much attention in the field of development of optical devices and high-power electronic elements due to high thermal stability and wide band-gap energy thereof. In particular, blue light emitting devices, green light emitting devices, UV light emitting devices and the like using nitride semiconductors are commercialized and have entered widespread use.
The light emitting device using such a nitride semiconductor may be implemented on a hetero-substrate made of materials such as sapphire or silicon carbide (SiC). As such, when nitride semiconductor thin films having a hetero-junction are grown using a sapphire substrate or other hetero-substrates or the like, differences in lattice mismatch and coefficient of thermal expansion caused by the hetero-junction may cause high crystal defects and high strain in thin films.
Regarding the nitride semiconductor thin films grown on a sapphire substrate, development of low-temperature gallium nitride (GaN) and low-temperature aluminum nitride (AlN) buffers and the like have been investigated in order to reduce dislocation generated on the substrate, such that defect density is reduced to some extent. However, the nitride semiconductor thin films still have a high defect density of about 108 cm−2.
In addition, when a hetero-junction is formed on a silicon (Si) substrate, dislocation density may still be high in spite of applying various thin film growth methods. In particular, in the process of cooling gallium nitride semiconductors grown at a high temperature to room temperature, there are problems associated with tensile strain applied to the thin film due to differences in coefficient of thermal expansion between the thin film and the Si substrate.
Meanwhile, although growth of nitride semiconductor thin films using a GaN substrate may be the most superior growth method developed to date, production methods of GaN substrates have technical problems hindering commercialization, and entail a cost several tens to several hundreds times the cost of hetero-substrates, such as sapphire or Si, in terms of economical efficiency, thus restricting widespread use of GaN as a substrate.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.